Automatic hole finder for spike driver

ABSTRACT

This is a method and apparatus for finding the hole in a tie plate by the use of reflected light and automatically driving the spike through the hole to secure the rail and tie plate to the tie so that operator error in spiking railroad track is eliminated.

O Unlted States Patent 11 1 1 1111 3,745,930 Dieringer 1 July 17, 1973 [54] AUTOMATIC HOLE FINDER FOR SPIKE 3,401,642 9/ 1968 Fisher 104/7 DRIVER 3,478,218 11/1969 Wuellner et a1. 250 223 3,117,480 1/1964 Peddinghaus 1 356/172 [75] Inventor: Andrew M. Dieringer, Waterford, 3,333,504 8/1967 Jones et al 356/172 Wis, 3,335,281 8/1967 Willits 356/172 1 3,489,909 1/1970 Martel 250/223 [73] Asslgnee- Rexmrd Inc-1 Mflwaukeewls- 2,479,293 8/1949 Bayless 250/234 22 Filed; June 7 1971 3,504,635 4/1970 Stewart et a1 104/12 [211 App! 150320 Primary Examiner-Gerald M. Forlenza Related [1.5. Application D ta Assistant Examiner-Richard A. Bertsch [63] Continuation of Ser. No. 805,780, March 10, 1969, McEachra" abandoned.

[57] ABSTRACT [52] US. Cl. l04/17l6l2bSg/92; This is a method and apparatus for finding the hole in [51] Int. Cl /23 a tie plate by the use of reflected light and aummati [58] new of Search :8 I 33 cally driving the spike through the hole to secure the 2 I l rai1 and tie plate to the tie so that operator error in spik- References Cited ing railroad track is eliminated.

UNITED STATES PATENTS 13 Claims, 3 Drawing Figures 3,260,851 7/1966 .lacobssonn, 250/223 PATENEB JUL 1 7 I973 I SHEET 2 BF 3 AUTOMATIC HOLE FINDER FOR SPIKE DRIVER This is a continuation of application, Ser. No. 805,780, filed Mar. 10, 1969, now abandoned.

This invention is in the field of spike driving machines for driving spikes into the ties in railroad track and is specifically concerned with a method and apparatus for automatically finding the hole in the tie plate, positioning the spike over thehole, and driving the spike through the hole in the tie plate and into the tie, all on an automatic basis.

A primary object of the invention is a method and apparatus for automatically finding the hole in the tie plate and driving the spike through it.

Another object is a method and apparatus of the above type which eliminates operator error.

Another object is a method and apparatus of the above type which leaves a minimum to the operators discretion or judgment.

Another object is a hole finding method and apparatus which insures that the spike will be accurately driven.

Another object is a hole finder which uses reflected light as the searching or scanning media.

Another object is a hole finding method which is selfcompensating so that variations and changes in the reflectivity of the surface being worked upon will be factored out.

Another object is a method and apparatus which automatically finds the hole in a tie plate and drives the spike much more rapidly and accurately than anything heretofore.

Other objects will appear from time to time in the ensuing specification and drawings in which:

FIG. 1 is a schematic of a spike driving mechanism with a reflected light apparatus;

FIG. 2 A is a portion of the electrical circuit; and

FIG. 2 B is another portion of the electrical circuit.

In FIG. 1, a spike driving mechanism has been indicated schematically at above a railroad track 12 where a rail 14 is supported on a tie plate 16 which in turn rests on a tie 18. In FIG. I, the side of the rail and the end of the tie are shown so that the view may be considered to be taken transversely of the general direction of the track.

ically in FIG. 1 which is intendedto represent any' power mechanism for driving spikes. In the diagrammatic form shown, the cylinder is mounted on a framework 22 of any suitable type which in turn carries jaws 24, shown as pivoted, to releasably hold a conventional spike 26. The mechanism may have a movable carriage mounted on the vehicle and constructed to be moved by any suitable power mechanism, such as a hydraulic cylinder 28, which may be assumed to move the carriage along with the spike driving mechanism 10 longitudinally of the rails. While the power source 28 for moving the carriage has been shown diagrammatically and not connected to the spiking carriage, it should be understood'that 28 is intended to represent any suitable power mechanism for swinging, sliding or otherwise positioning some sort of a carriage spiking mechanism the details of which in and of themselves are unimportant.

For a typical example of a conventional spike driver, see U.S. Pat. No. 3,426,698, issued Feb. 11, 1969, and assigned to the assignee of the present application.

A light source 30 of any suitable type has been shown mounted on the carriage so that it moves with it. The general direction of the light from the source is at a decided angle to the upper surface 32 of the tie plate. A sensing mechanism 34 is mounted on the carriage which includes a light control sensor 36 and a trigger sensor 38. As explained hereinafter, the light control sensor 36 sees a substantial area 40 of the reflecting surface of the tie plate and is set for a certain luminosity. If the condition of the reflected surface is such that the luminosity received by the light control sensor 36 varies from the predetermined setting, the light control sensor will turn the light 30 either up or down, i.e.,

modulates it so that the light reflected from the top of the tie plate will always be at the same level of intensity or luminosity. Various factors can cause the reflected light to vary, for example the tie plate may be new, old, rusty, wet or otherwise. The spike driver may be operating on a clear day or it may be overcast. The bulb in source 30 may be old or otherwise. The lamp or lense may be dusty. The point is that the sensor 36 wants a certain level of luminosity and it functions to turn the light 30 up or down until it gets what it wants.

The reason for this is so that the trigger sensor 38 will always receive the same level of luminosity regardless of any of the above factors. The trigger sensor is directed toward a more or less confined area 42. The spike and its driving gun are aligned generally with the spot 42 that the trigger sensor responds to. The mechanism is calibrated so that a certain drop in the luminosity received'by the trigger sensor 38, i.e., the shadow 44 in a hole 46 in the tie plate, will cause the heretofore described mechanism to stop the transverse of the carriage and drive the spike 26 into the spike hole in the tie plate and into the tie.

In FIGS. 2A and 28, a circuit has been shown which includes a suitable power source 48 connected to a power on button Sw-l with contacts 50, 52 and 54, all in a control box indicated generally by the dotted line 56. The operator presses control button SW-l momentarily and releases it, which is sufficient to put cur rent through the holding relay 58 which holds contacts 50 and 52 closed and contacts54 in the lower position. The holding solenoid may be released by a stop? button '55. Closing of the lowercontacts 54 energizes line 60, connection '60, 62, line64, light control sensor 36 (FIG. 2B),-trigger sensor 38,,light control circuit 66 (FIG. 2A) through connection 68.. At the same time, the light source 30 is energized through connection 70, and connection 72 which runs to the other side of the light control circuit 66. The trigger sensor 38 is also connected by a lead 74 to a trigger circuit 76 which is energized when the power button SW-l is momentarily depressed by the operator. Closing of the top contacts 50 of SW-l also energizes a relay K-2 through a line 78, which closes contacts 80, 82 and the lower contacts of 84. The lower contacts lead to a ram limit switch SW-3 with contacts 86 through a lead 88, which in turn is connected to a ram up" solenoid 90 through lead 92 with the .ram up solenoid 90 controlling hydraulic fluid to the ram 20 to raise it. When relay K-2 is energized, the upper contacts of 84 open, which opens a line 94 to a drive solenoid 96for the ram. When the "drive solenoid 96 is energized,- it will reverse the solenoid valve controlling the hydraulic fluid to the ram 20 so that the ram will be lowered to drive a spike. Thus the drive solenoid 96 lowers the ram to drive a spike while the ram up solenoid raises the ram or spike gun. Depressing the on button SW-l closes relay K-2 which energizes ram up solenoid 90 to raise the ram, if it is not already raised, and deenergizes the ram drive solenoid 96.

Carriage 22 has a limit switch SW-4 (FIG. 2B) with contacts 98 which connect to the middle contacts 82 of relay K-Z through a line 100 with the other side of SW4 contacts 98 being connected to a carriageback solenoid 102 through a line 104. A carriage forward solenoid 106 is connected by a lead 108 to the upper contacts 110 of a relay K-l, the lower contacts being designated 112.

When the power on button SW-l is initially depressed, the traversing carriage 22 should be fully retraeted, either left or right in FIG. 1, and the spike driving ram or gun 20 should be all the way up. If the carriage 22 is not fully withdrawn, contacts 98 of the carriage limit switch SW-4 will be closed which will energize the carriage back solenoid 102 which in turn will operate a suitable valve to energize the carriage traversing mechanism 28 which will return the carriage to its fully retracted position. When the carriage reaches its fully retracted position, contacts 98 of limit switch SW4 will open and opposing contacts 114 will close, which is the position shown in FIG. 2B.

The same is true of the spike driving mechanism or ram 20. If it is not in its fully raised position, the contacts 86 of the ram limit switch SW-3 will be closed which will energize the ram up solenoid 90. This in turn will control the ram actuating mechanism 20 to raise the ram. When the ram is all the way up, contacts 86 of limit switch SW-3 will open and the opposing contacts 116 will close, which is the position shown in FIG. 28. Contacts 116 f-SW-3 and 114 of SW-4 are in series by a lead 118 with the other side of contacts 114 being connected by a lead 120 to the middle contacts 112 of relay K-l (FIG. 2A).

If the ram is not fully retracted and if the carriage is not fully withdrawn, or both, the mechanism cannot be energized by the light arrangement. The first thing that will happen, when the on power button SW-l is depressed by the operator, is that the carriage will move to its fully retracted position and the ram will move to its fully raised position if they are not already there.

The machine is now ready to cycle. The operator depresses momentarily a cycle actuation button SW-2 (FIG. 2A) which is connected through a lead 122 to contacts 116 of limit switch SW-3 and contacts 114 of limit switch SW-4. If either or both of these contacts are open when the operator depresses the cycle actuation button SW-2, nothing will happen.

The light control sensor 36 automatically turns the light 30 either up or down through the light control circuit 66 until the exact amount of luminosity, as called for by the light control circuit 66, is received by the light control sensor 36. It will be recalled that whatever that luminosity setting is, the trigger sensor 38 will be receiving it. When the light control sensor sees" the proper amount of light, it will energize the base of transistor 123 in the trigger circuit through line 64 which in turn energizes relay K-l closing contacts 110 and the lower contacts of 112. The closing of contacts 110 energizes the carriage forward" solenoid 106 through line 108. This starts the carriage traversing, for example in the direction of the arrow in FIG. 1. The confined luminous spot 42 detected by the trigger sensor 38 then may be assumed to be moving from left to right in FIG. 1. As soon as the luminosity of spot 42 drops due to the shadow 44 in the spike hole 46 in the tie plate, this puts more resistance in series with the trigger circuit 76, which deenergizes transistor 123 opening up relay K-l and breaking contacts 110 and the lower contacts of 112. Note that this closes the upper set of contacts of 112 which energizes the ram drive" solenoid 96 through line 94 and the upper contacts of 84. The ram or gun 20 (FIG. 1) lowers the spike 26 into the tie plate hole 46 and drives it into the tie 18. A pressure limit switch 126 is arranged to react to a certain pressure build-up in the ram, for example 2,000 psi. When the pressure in the ram reaches whatever point is selected, switch 126 closes. The pressure limit switch contacts are connected by a lead 128 to the upper contacts of 112 of relay K-l and a second lead 130 which energizes relay K-2 pulling all of the contacts 80, 82 and 84 down and breaking the upper contacts of 84 which deenergizes line 94 and drive solenoid 96. Since the carriage is not in its fully retracted position, as is the ram, contacts 116 and 1 14 of limit switches SW-3 and SW-4 are open. The closing of contacts and 82 when relay K-2 is energized energizes the carriage back solenoid 102 through contacts 98 of limit switch SW-4 (which are closed) and the ram up solenoid through contacts 86 of limit switch SW-3 (which are closed). Thus the closing of contacts 126 by the build up of pressure in the ram driving system, at whatever point is selected in pressure build-up, automatically energizes the ram raising and carriage retracting mechanisms. And the sequence of operations is ready to start over again. The unit may have a manual carriage traversing button 127, if desired.

In FIG. 1, the spike being driven into the tie plate hole and tie may be considered to be either between the rails or outboard. Longitudinal movement of the carriage and spike is adjusted, lined up and fixed with the flange on the wheel of the spike driving vehicle being gauged laterally to the position of the spike hole which is sufficiently accurate. If there is any minor lateral misalignment, the bottom of the spike is pointed or chiseled, as indicated at 131, in a longitudinal direction so that the spike will automatically cam through the minor misalignment and will enter the tie plate hole properly. Thus carriage movement to find the tie plate hole and drive the spike is basically in a longitudinal direction which may be considered generally parallel to the track. Since the holes in a tie plate are accurately spaced, a similar carriage might work the other side of a rail with the gauging being set between carriages. One reflected light system, either inside or outside, could fine one tie plate hole and two spikes could be driven simultaneously with the gauge of the tie plate holes being automatically fixed in the spacing of the driving guns 20.

Or you might have the inside and outside carriage completely independent of each other with each having its own reflected light system and operating totally independently, a connection for the other being shown at 132 in FIG. 2A.

Whereas only one axis traversing has been shown, it should be understood that two-axis traversing could be used, if desired, in which case the light and sensors might be disposed at more or less a 45 angle to the track and to the tie plate holes to establish a rectangular shadow in the hole. But it is preferred that the carriage be gauged to the rail head and fixed and that all scanning be in one direction or along one axis only.

The use, operation and function of the invention are as follows:

A reflected light system is used to sense, detect and pick up the holes in a working surface, shown in this case as tie plate holes in a tie plate so that a spike or any other suitable working instrument may be automatically positioned relative to the hole and then work performed. This takes the form of driving a spike into the hole, but it might be a drill to drill a hole in the tie. I have referred to a spike as being driven, but it might also be a positioning pin or dowl. Whether the working instrument is a spike which is driven or a drill, reamer, tap or what have you, the point is that light is projected toward the working surface at a decided angle so that a shadow will be created in the hole. A light sensor is disposed to pick up the reflected light from the working surface and where the luminosity drops due to the shadow produced in the hole, the light sensor will feed back a control to the working mechanism and perform a working operation in response thereto.

An important aspect of the invention is the light control sensor which observers a defined area of the luminated surface and is set for a certain level of reflected light. If it doesnt see that level, it automatically turns the light up or down until the desired level of reflected light is obtained. Thus the sensor unit which is preferably adjacent to the level sensor will al ways be receiving the same level or intensity of reflected light from the working surface, in this case the top of the tie plate. The sensor can in turn be set at the selected level of reflected light and as soon as the received luminosity drops due to the shadow in the hole, the sensor energizes or deenergizes the various mechanisms described previously.

When used in the railroad field, specifically on a spike driver, the invention has the advantage that the operator of the spike driver merely positions his machine roughly over the tie .plate and then depresses the cycle actuated button, in this case SW-2, which starts the traversing or scanning movement. The operator then no longer controls the sequence of steps and the predetermined level, stops, automatically retracts, re-- traverses the carriage back to the starting point and is ready for another cycle. The operator cannot influence or affect the scanning and spike driving and the system automatically insures that the hole is found and the spike is properly driven. This greatly reduces or completely eliminates bent spikes which have been a never ending source of expense and troubles.

While the preferred form of the invention has been shown and described and several variations have been suggested, it should be understood that numerous additional modifications, substitutions, changes and alterations may be made without departing from the inventions fundamental theme.

I claim:

l. A method of doing work in a hole in a work piece having an exposed surface, including the steps of positioning a working instrument in working relation to the exposed surface, directing a light beam at the exposed surface at an angle that will produce a shadow in the hole, sensing the light reflected from the exposed surface, adjusting the intensity of the light beam so that the light reflected from the exposed surface will always be at the same level of intensity regardless of changes in the reflectivity of the exposed surface, independently sensing the reduction in the reflected light caused by the shadow in the hole, and energizing the working instrument in response to the reduction in the reflected light caused by the hole to do work in the hole.

2. A method of driving a spike into a hole in a tie plate and into a tie, including the steps of positioning a spike in working relation to the top of the tie plate, directing a light beam at the top of the tie plate at an angle that will produce a shadow in the hole, sensing the light reflected from a limited area on the top of the tie plate, aligning the spike with and above the limited area of the tie plate, traversing the spike, the limited area, and the sensing step above the tie plate in a generally horizontal direction, detecting the reduction in the light reflected from the top of the tie plate caused by the shadow in the hole, stopping the horizontal move ment of the spike over the hole in the tie plate in response to a reduction in the reflected light caused by the shadow in the hole, and driving the spike downwardly through the hole in the tie plate and into the tie.

3. The method of claim 2 further characterized by and including the steps of gauging the distance of the spike from the head of the rail, and traversing the spike above the tie plate in a generally horizontal direction at the gauged distance from the rail.

4. The method of claim 2 further characterized by and including the steps of separately sensing the light reflected from the top of the tie plate in an area adjacent the limited area, and adjusting the intensity of the light beam in response to the separate sensing step so that the light reflected from the top of the tie plate will always be at the same level of intensity regardless of changes in the reflectivity of the top of the tie plate.

5. The method of claim 2 further characterized by and including the step of simultaneously driving a second spike in a second hole in the tie plate by moving the second spike through the various steps at a gauged distancefrom the first spike corresponding to the distance between the holes in the tie plate so that the second spike will automatically be aligned with and driven into the second hole.

6. The method of claim 2 further characterized in that the step of driving the spikedownwardly through the hole in the tie plate is automatically initiated in response to the detection of the shadow in the hole.

7. [n a device for doing work in a hole in a work piece having an exposed surface, a working instrument positioned in working relation to the exposed surface of the work piece, means for directing a light beam at the exposed surface at an angle that will produce a shadow in the hole, sensing means for sensing the light reflected from the exposed surface, adjusting means responsive to the sensing means for adjusting the intensity of the light beam so that the light reflected from the exposed surface will always be at the same level of intensity regardless of changes in the reflectivity of the exposed surface, and a second sensing means for independently sensing the reduction in the reflected light caused by the shadow in the hole for energizing the working instrument and causing it to do worlk in the hole.

8. In a device for driving railroad spikes into the holes in tie plates in railroad tracks, a spike driving mechanism disposed for generally vertical movement aligned with a certain position, means for directing a light beam at an angle to the top of the tie plate that will produce -a shadow in the hole in the tie plate, sensing means the hole for energizing the spike driving mechanism to drive a spike into the hole in the tie plate and into the tie.

9. The structure of claim 8 further characterized by and including a second sensing means aligned with a second position on the top of the tie plate adjacent the said certain position for detecting the light reflected therefrom, and means responsive to the second sensing means for adjusting the intensity of the light beam so that the light reflected from the surface of the tie plate will always be at the same level of intensity regardless of changes in the reflectivity of the top of the tie plate.

10. The structure of claim 8 further characterized by and including traversing means for moving the spike driving mechanism and the sensing means over the tie plate in a scanning motion, and means for automatically de-energizing the traversing means when the sensing means detects a reduction in the reflected light due to the shadow in the hole in the tie plate, and for automatically energizing the spike driving mechanism at the same time.

11. The structure of claim 10 further characterized by and including means for automatically retracting the spike driving mechanism when a predetermined spike driving pressure has been reached.

12. In a device for driving spikes into the holes in tie plates and into the ties in railroad track, a frame movable along a railroad track, a carriage movably mounted on the frame between a withdrawn position and an extended position so that it may perform a generally horizontal scanning motion, a power operated spike driver on the frame constructed to perform a generally vertical up-and-down spike driving motion along a defined path, a light source on the frame directed at an angle to the top of the tie plates so that it will create a decided shadow in the tie plate holes, a sensing mechanism on the carriage directed at the location where the defined path of the spike driver will intersect the top of the tie plate and mounted on the carriage so that it will perform the scanning step therewith, carriage power means for moving the carriage and sensing mechanism through their scanning motion, and automatic means for energizing the spike driver responsive to the sensing mechanism detecting a shadow in the tie plate hole and, at the same time, for de-energizing the carriage power means so that sensing will stop.

13. The structure of claim 12 further characterized in that the light source is mounted on the carriage and is movable therewith during scanning. 

1. A method of doing work in a hole in a work piece having an exposed surface, including the steps of positioning a working instrument in working relation to the exposed surface, directing a light beam at the exposed surface at an angle that will produce a shadow in the hole, sensing the light reflected from the exposed surface, adjusting the intensity of the light beam so that the light reflected from the exposed surface will always be at the same level of intensity regardless of changes in the reflectivity of the exposed surface, independently sensing the reduction in the reflected light caused by the shadow in the hole, and energizing the working instrument in response to the reduction in the reflected light caused by the hole to do work in the hole.
 2. A method of driving a spike into a hole in a tie plate and into a tie, including the steps of positioning a spike in working relation to the top of the tie plate, directing a light beam at the top of the tie plate at an angle that will produce a shadow in the hole, sensing the light reflected from a limited area on the top of the tie plate, aligning the spike with and above the limited area of the tie plate, traversing the spike, the limited area, aNd the sensing step above the tie plate in a generally horizontal direction, detecting the reduction in the light reflected from the top of the tie plate caused by the shadow in the hole, stopping the horizontal movement of the spike over the hole in the tie plate in response to a reduction in the reflected light caused by the shadow in the hole, and driving the spike downwardly through the hole in the tie plate and into the tie.
 3. The method of claim 2 further characterized by and including the steps of gauging the distance of the spike from the head of the rail, and traversing the spike above the tie plate in a generally horizontal direction at the gauged distance from the rail.
 4. The method of claim 2 further characterized by and including the steps of separately sensing the light reflected from the top of the tie plate in an area adjacent the limited area, and adjusting the intensity of the light beam in response to the separate sensing step so that the light reflected from the top of the tie plate will always be at the same level of intensity regardless of changes in the reflectivity of the top of the tie plate.
 5. The method of claim 2 further characterized by and including the step of simultaneously driving a second spike in a second hole in the tie plate by moving the second spike through the various steps at a gauged distance from the first spike corresponding to the distance between the holes in the tie plate so that the second spike will automatically be aligned with and driven into the second hole.
 6. The method of claim 2 further characterized in that the step of driving the spike downwardly through the hole in the tie plate is automatically initiated in response to the detection of the shadow in the hole.
 7. In a device for doing work in a hole in a work piece having an exposed surface, a working instrument positioned in working relation to the exposed surface of the work piece, means for directing a light beam at the exposed surface at an angle that will produce a shadow in the hole, sensing means for sensing the light reflected from the exposed surface, adjusting means responsive to the sensing means for adjusting the intensity of the light beam so that the light reflected from the exposed surface will always be at the same level of intensity regardless of changes in the reflectivity of the exposed surface, and a second sensing means for independently sensing the reduction in the reflected light caused by the shadow in the hole for energizing the working instrument and causing it to do work in the hole.
 8. In a device for driving railroad spikes into the holes in tie plates in railroad tracks, a spike driving mechanism disposed for generally vertical movement aligned with a certain position, means for directing a light beam at an angle to the top of the tie plate that will produce a shadow in the hole in the tie plate, sensing means aligned generally with the said certain position for sensing the light reflected from the top of the tie plate at the said certain position, and means responsive to the reduction in the light reflected from the said certain position on the top of the tie plate caused by the shadow in the hole for energizing the spike driving mechanism to drive a spike into the hole in the tie plate and into the tie.
 9. The structure of claim 8 further characterized by and including a second sensing means aligned with a second position on the top of the tie plate adjacent the said certain position for detecting the light reflected therefrom, and means responsive to the second sensing means for adjusting the intensity of the light beam so that the light reflected from the surface of the tie plate will always be at the same level of intensity regardless of changes in the reflectivity of the top of the tie plate.
 10. The structure of claim 8 further characterized by and including traversing means for moving the spike driving mechanism and the sensing means over the tie plate in a scanning motion, and means for automatically de-energIzing the traversing means when the sensing means detects a reduction in the reflected light due to the shadow in the hole in the tie plate, and for automatically energizing the spike driving mechanism at the same time.
 11. The structure of claim 10 further characterized by and including means for automatically retracting the spike driving mechanism when a predetermined spike driving pressure has been reached.
 12. In a device for driving spikes into the holes in tie plates and into the ties in railroad track, a frame movable along a railroad track, a carriage movably mounted on the frame between a withdrawn position and an extended position so that it may perform a generally horizontal scanning motion, a power operated spike driver on the frame constructed to perform a generally vertical up-and-down spike driving motion along a defined path, a light source on the frame directed at an angle to the top of the tie plates so that it will create a decided shadow in the tie plate holes, a sensing mechanism on the carriage directed at the location where the defined path of the spike driver will intersect the top of the tie plate and mounted on the carriage so that it will perform the scanning step therewith, carriage power means for moving the carriage and sensing mechanism through their scanning motion, and automatic means for energizing the spike driver responsive to the sensing mechanism detecting a shadow in the tie plate hole and, at the same time, for de-energizing the carriage power means so that sensing will stop.
 13. The structure of claim 12 further characterized in that the light source is mounted on the carriage and is movable therewith during scanning. 